Hydrofoil watercraft having stabilizing means



y 7, 1957 B. K. L. ALMQVIST EI'AL 2,791,195

HYDROFOIL WATERCRAFT I'IAVING STABILIZING MEANS Filed Nov. 15. 1954 J INVENTORS- 8O KARL L. ALMQVIST I Q 3Q aJbim OLOF ELGSTRUM ATTORNEYS United States Patent ce HYDROFOIL WATERCRAFT HAVING STABILIZING MEANS Bo Karl Loritz' Ahnqvist and Bjiirn Olaf Elgstriim, Den

Haag, Netherlands, assignors to International Aquavron S. A., Casablanca, Morocco, a body corporate of Morocco Application November 15, 1954, Serial No. 468,868 Claims priority, application Sweden November 19, 1953 9 Claims. (Cl. 114--=66.5)

The present invention refers to a hydrodynamically lifted watercraft and is substantially characterized in that the principal weight of the craft when under way is carried by a dynamically lifting system comprising at least one hydrofoil, the upwardly directed resulting force of which is located at, or somewhat astern of, the normal centre of gravity of the craft, whereas the rest of the weight is supported by one (or several) sliding surfaces arranged ahead of said centre and bearing a small load: in addition a stabilizer is mounted astern of the dynamically lifting system and preferably far aft in the craft; this stabilizer is immersed in the water like a hydrofoil and in the normal position of the craft under way is substantially unloaded. Both hydrofoil and stabilizer are preferably rigidly secured to the hull of the craft. The craft is preferably designed so that, when stationary, its displacement is distributed over two or several hulls or over longitudinally extending floats assembled by a bridge. The hydrofoil and the stabilizer are arranged between the side floats and the hydrofoil may be entirely arranged between planes passing through the side surfaces of the craft so that no portion of this hydrofoil projects out of these side planes.

The invention will be described more in detail with reference to an embodiment given by Way of example and illustrated in the annexed drawing.

Fig. 1 shows the craft in elevation, and Fig. 2 shows a section on line 11-11 in Fig. 1.

Fig. 3 shows an alternative form of the stabilizer arrangement, i

Fig. 4 is a transverse section along line IV'-IV of Fig. 1 showing an alternative form of the bow part of the craft.

In this example, the craft consists of two boat hulls or of two longitudinally extending floats 1 united by a rigidly secured bridge 2, which preferably forms a tight bottom between the floats, and preferably extends over the whole or the major part of the length of the craft. In the example illustrated, the floats have a V-shaped bottom. Each float has a forward part 3, for instance in the shape of a V-stem, which is separated from the other part of the float by a step 4. If desired, this forward part may be common to both floats, so that the step 4 will extend crosswise over the craft (Fig. 4).

The bottom surface 5 immediately in front of the step is substantially plane and forms a glider plane.

When under way, the floats, with the exception of the sliding surface 5, are entirely raised above the surface of the water and the craft is supported by a dynamic system, which in the example shown is formed by a hydrofoil 6, of the conventional type, for instance. The hydrofoil, which is preferably of the self-stabilizing, in other words of the laterally stabilizing, type, is secured to the floats 1, and preferably is made all of a piece and extends transversely below the craft, but without any portion extending outside the sides of the craft.

The upwardly directed resulting force p of the hydro- 2,791,195 Patented May 7, 1957 foil or hydrofoils is located at or preferably immediately ing force, p, should preferably be located so near the centre of gravity T that the sliding surface 5 bears only a very small load, as it is advantageous, inter alia, for its gliding ability along the water surface V, on which it glides when under way. However, on account of this low normal load on the glider plane, the running of the craft, when in the position lifted above the water, becomes sensitive to the alterations of the location of the load; For this reason, a stabilizer 7 is arranged astern of the hydrofoil system, preferably far abaft in the craft; this stabilizer is substantially unloaded when the craft is in its normal position (that is to say, is under Way) and does not stand at an angle to the surface of the water. The stabilizer may be symmetrical in longitudinal section.

Obviously, the stabilizer will, for instance if an alteration of the position of the centre of gravity T is caused by a displacement of the load with a consequent tendency of the craft to take a fore-and-aft inclination to the horizontal plane and thus to deviate from the normal, assume a corresponding inclination, and stand at a compensating angle to the water so as to tend to restore the normal condition. In the same way, the stabilizer will have a damping effect on the fore-and-aft oscillations caused by the motion of the waves.

Preferably, the stabilizer is rigidly secured to the craft, but it may be made movable, if desired. For example, it may be swingabiy mounted on a transversely extending axis provided at its fore edge so as to be able to swing, preferably freely, and in this case one or two, preferably adjustable, stop members are provided to limit the up ward and downward oscillatory motions, or only the upward motion.

For instance, as shown in Fig. 3, the stabilizing member 7 is pivoted near its fore edge on a transverse axis 8 supported by lateral members 9 and connected near'its rear edge by a pivoted lever 10 with a vertically sliding stem 11 provided with a stop member 12 cooperating with two abutments 13, 13', the stabilizing member being substantially horizontal in its lowest position.

What we claim is:

1. A hydrodynamically lifted water-craft having a hull and comprising in combination a hydrodynamic lifting system comprising at least one hydrofoil means disposed below said hull so as to support the major part of the weight of the craft substantially at the normal center of gravity of the craft; skidding means having at least one skidding surface arranged forward of said center of gravity; and automatically actuated stabilizer means arranged astern of said hydrodynamic lifting system and formed by a hydrofoil like immersed member disposed to be substantially unloaded in the normal position of movement of the craft, said stabilizer means comprising an immersed hydrofoil-like member having an angle of incidence substantially equal to zero in the normal position of the craft during its movement.

2. A hydrodynamically lifted water-craft having a hull and comprising in combination a hydrodynamic lifting system comprising at least one hydrofoil disposed below said hull so as to have its upwardly directed resultant force applied to a point located substantially at the normal center of gravity of said craft, said hydrodynamic lifting system being arranged to normally support the major part at the weight of the craft; at least one skidding surface arranged forward of said center of gravity below said hull and supporting a small load constituting the remaining weight of the craft; and an immersed stabilizer formed by a hydrofoil-like member arranged astern of said hydrodynamic lifting system and having normally an angle of incidence substantially equal to zero so as to be substantially unloaded in the normal position of the craft during its movement.

3. A hydrodynamically lifted water-craft having a hull and comprising in combination a hydrodynamic lifting system comprising at least one hydrofoil disposed below said hull so as to have its upwardly directed resultant force applied to a point located substantially slightly astern of the normal center of gravity of said craft, said hydrodynamic lifting system being arranged to normally support the major part of the weight of the craft; at least one skidding surface arranged at the forward end of said hull and supporting a small load constituting the remaining weight of the craft; and an immersed stabilizer formed by a hydrofoil-like member arranged far abaft in said craft and having normally an angle of incidence substantially equal to zero so as to be substantially unloaded in the normal position of the craft during its movement. i

4. A hydrodynamically lifted watercraft according to claim 2 wherein said stabilizer is rigidly secured to the hull.

5. A hydrodynamically lifted watercraft according to claim 2 wherein said stabilizer is freely pivotably mounted on the hull about a transverse axis in the vicinity of its forward edge, stops being provided to limit the oscillations of said stabilizer.

6. A hydrodynamically lifted watercraft comprising a hull provided at its forward end with a V-shaped bow part having a bottom surface being substantially planar.

toward the rear end thereof, said surface forming a skidding surface supporting a small fraction of the weight of the craft, said bow part forming an upwardly and rearwardly curved step at the junction between said bow part and the remaining part of the bottom of the hull, a hydrofoil having the shape of a flat U being rigidly attached to the lateral Walls of the hull slightly astern the center of gravity thereof and an immersed stabilizer formed by a hydrofoildike U-shaped member and rigidly secured to the hull far abaft in the craft, the immersed part of said stabilizer having normally an incidence angle equal to zero so as to be substantially unloaded under normal conditions of operation of the craft.

7. A hydrodynamically lifted watercraft comprising at least two longitudinally extending floats, a bridge rigidly mounted on said floats, V-shaped bow parts at the for ward ends of said floats having a bottom skidding surface being substantially planar toward the rearward end thereof, said bow parts forming upwardly and rearwardly curved steps at the junction between said bow parts and the remaining parts of the respective floats, a hydrofoil shaped as a fiat U arranged in the middle part of the watercraft and extending from the outermost float on starboard to the outermost float on port and rigidly secured to the lateral faces of said floats respectively, immersed stabilizing means arranged further to the rear of the watercraft and formed by a hydrofoil-like member having in normal conditions of forward movement of the craft an angle of incidence equal to zero.

8. A hydrodynamically lifted watercraft comprising at least two longitudinally extending floats, a bridge rigidly mounted on said floats, a V-shaped common bow part at the forward end of said floatshaving a bottom skidding surface being substantially planar toward the rear end thereof, said bow part forming an upwardly and rearwardly curved step at the junction between said how part and the bottom of said floats, a hydrofoil shaped as a fiat U arranged in the central part of the watercraft and extending from the outermost float on starboard to the outermost float on port and rigidly secured to the lateral faces of said fioats respectively, immersed stabilizing means arranged further to the rear of the watercraft and formed by a hydrofoil-like member having in normal condition of forward movement of the craft an angle of incidence equal to zero.

9. In a hydrodynamically lifted watercraft having a hull the improvement of, in combination, a hydrodynamic lifting system comprising at least one hydrofoil means disposed below said hull so as to support the major part of the weight of the craft substantially at the normal center of gravity of the craft; skidding means having at least one sliding surface arranged forward of said center of gravity; and automatically actuated stabilizer means arranged astern of said hydrodynamic lifting system.

References Cited in the filc of this patent UNITED STATES PATENTS 1,355,736 Curtiss Oct. 12, 1920 2,491,744 Link Dec. 20, 1949 2,696,796 Amster Dec. 14, 1954 2,713,317 Herz July 19, 1955 FOREIGN PATENTS 19,496 Great Britain of 1907 OTHER REFERENCES Serial No. 268,421, Tietjens (A. P. C.), published May 11, 1943. 

